The International Space Station (ISS) is a little homier now thanks to its new aquarium. This addition isn't just intended to brighten up the lunch room - it’s a serious piece of experimental hardware built by the Japanese Space Agency (JAXA) and delivered the the ISS on Friday, July 27, 2012 by the unmanned Japanese cargo ship, Kounotori3 (HTV3). The special aqueous habitat will be used to study the effects of the space environment on marine life.

The Aquatic Habit (AQH) is a high-tech aquarium designed to operate in zero gravity. It requires a minimum of maintenance by the crew (it even feeds the fish itself) and can eventually be used to house amphibians as well as fish. It’s not the first such habitat in space. Earlier examples flew on space shuttle missions STS-47, STS-65 and STS-90. However, this is the first to be installed aboard a space station. Sitting in a standard payload rack in the Japanese Experiment Module (JEM), the AQH is sealed, self-contained unit with a closed-water circulatory system.

The AQH is actually made up of two chambers for habitation that measure 15 cm x 7 cm x 7 cm (5.9 x 2.8 x 2.8 inches) and holds approximately 700 cc (23.6 oz) of water. Learning lessons from previous versions, the AQH has a more advanced life support system that not only circulates water, but constantly monitors conditions in the habitat. Waste is automatically removed, pressure levels and oxygen levels maintained and temperature regulated.

“In order to keep water quality in good condition for the health of the fish, we had to do many tests on the filtration system, especially the bacteria filter," said Nobuyoshi Fujimoto, associate senior engineer at JAXA's Space Environment Unitization Center. "The special bacteria filter purifies waste materials, such as ammonia, so that we can keep fish for up to 90 days. This capability will make it possible for egg-to-egg breeding aboard station, which means up to three generations may be born in orbit. This would be a first for fish in space."

The astronauts don’t even need to feed the fish the occasional ant’s egg. An automatic system handles that as well. It’s LED lights are programmed to simulate night and day conditions and there is a specimen removal mechanism. Two video cameras in the unit allow the fish to be monitored from the Earth.

One particularly notable innovation is the “air-water interface.” This is made up of small plastic plates in the top of the tanks that use a grid to trap bubbles of air. If the AQH is successful, this will allow amphibians to fly on future missions.

What’s it for?

On this mission, fish are the center of attention. Along with the AQH, there were a number of freshwater Medaka fish (Oryzias latipes) that traveled to the station in a special container. Medaka fish are a small fish commonly found in rice paddies in Asia and are regarded as ideal specimens for study. They and their eggs are transparent, which makes it easy to study their insides, they have a very fast breeding cycle, will breed in zero gravity and their genome has already been mapped, so studies of genetic changes due to radiation can be done easily.

The 90 day study will focus on the effects of radiation on bone degradation and genes, muscle atrophy and developmental biology - some of which may lead to better understandings of human health issues.

"We think studies on bone degradation mechanisms and muscle atrophy mechanisms are applicable to human health problems, especially for the aging society," said Fujimoto.

Source: NASA